Studies have been made to formulate a softening base agent in a detergent to prevent washed fiber products from losing softness into ones having a stiff feel caused by, for example, the elimination of a fiber treating agent and the adsorption of salts. For example, it has been known to formulate a clay mineral such as smectites (see, for example, JP-A 49-85102), a cationic surfactant such as a dialkyl type quaternary ammonium salt (see, for example, Publication of The Patent Office, Known and Customary Technological Collection (Powder detergents for clothes), published on Mar. 26, 1998) or silicon such as polydimethylsiloxane (for example, JP-A 2002-249799).
Also, studies have recently made as to a method of reinforcing the softening effect given by a clay mineral from the viewpoint of for example, formulating with ease and environment response. For example, it has been known to combine bentonite and a pentaerythritol compound (see, for example, JP-A 5-140869), a clay mineral and a coagulant (see, for example, JP-A 2002-541342) and bentonite and a soluble potassium salt (see, for example, JP-A 8-506843.